Online collaboration is continuously becoming cheaper, faster, and easier to achieve. People at different physical locations can now collaborate online via shared workspaces which allow them to share content instantly with anyone as well as viewing and editing shared contents. An example of an online collaboration system is a document proofing and approval system which allows a group of document reviewers to each review and comment on a single document, before a final version can be agreed upon.
As these online collaboration systems become more and more popular, users become more accustomed to use such systems to share confidential and important data over the internet. The risk associated with sharing important data online is obvious—the communication can be eavesdropped during data transfer over public communication networks. The content can then be readily viewed by the intruder. Even if the data is stored on the server and not being transferred over public communication networks, the server may be hacked which means the data stored is at risk of being exposed and compromised.
To protect the data stored on a computer, cryptographic systems are developed to encrypt the data before it is stored. A cryptographic system protects data by encrypting it with a key. If the encryption algorithm is strong and the key is chosen carefully, then it is more difficult to recover the original data content without the key. The encrypted data can only be viewed by a user with the correct decryption key. Although such systems improve the security of data storage systems, it is not suitable and often cumbersome to use in a collaborative environment where data stored on the server needs to be accessed or viewed by a plurality of users as this requires the encryption and decryption keys to be distributed to all authorized users.
In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.